可重复使用飞行器进场着陆拉平纵向控制

针对可重复使用飞行器（RLV）进场着陆拉平段的纵向控制问题,提出了反馈控制与前馈控制相结合的复合控制策略。设计反馈控制律参数,在此基础上基于时间加权高度跟踪误差/误差变化率平方积分指标优化设计前馈控制律参数。按输入补偿的前馈控制在不影响系统稳定性的前提下,提高了RLV对拉平着陆轨迹的跟踪精度,减小了RLV的接地散布。提出了基于积分器初值的控制律平滑切换方法,实现了RLV起落架释放前后不同控制律之间的平滑切换。仿真验证了拉平纵向复合控制和拉平过程中不同控制律之间平滑切换方法的有效性。      

采用弱攻角补偿与脱敏设计的火星进入段制导

为提升火星进入段存在多种扰动时的制导末端精度,在现有三自由度脱敏设计的基础上,提出针对大气密度及升阻力系数波动的弱攻角补偿方法。通过攻角调整,协调升、阻力加速度测量值相对理论计算值的偏离程度,使加权形式的偏离程度指标趋近于1,从而降低气动参数波动对制导精度的影响。相平面分析和反证法证明了攻角调整过程的稳定性。蒙特卡洛仿真结果表明,该方法可达到较高的纵向末端状态精度。     

A method of multi-objective reliability tolerance design for electronic circuits

Tolerance design plays an important role in reliability design for electronic circuits. The traditional method only focuses on the consistency of output response. It is not able to meet the needs of increasing development of electronic products. This paper researches the state of related fields and proposes a method of multi-objective reliability tolerance design. The characteristics of output response and operating stresses on critical components are both defined as design objectives. Critical components and their operating stresses are determined by failure mode and effect analysis (FMEA) and fault tree analysis (FTA). Sensitivity analysis is carried out to determine sensitive parameters that affect the design objectives significantly. Monte Carlo and worst-case analysis are utilized to explore the tolerance levels of sensitive parameters. Design of experiment and regression analysis are applied in this method. The optimal tolerance levels are selected in accord with a quality-cost model to improve consistency of output response and reduce failure rates of critical components synchronously. The application in light-emitting diode (LED) drivers indicates details and potential. It shows that the proposed method provides a more effective way to improve performance and reliability of electronic circuits.     

Environmental stress level evaluation approach based on physical model and interval grey association degree

 Associating environmental stresses (ESs) with built-in test (BIT) output is an important means to help diagnose intermittent faults (IFs). Aiming at low efficiency in association of traditional time stress measurement device (TSMD), an association model is built. Thereafter, a novel approach is given to evaluate the integrated environmental stress (IES) level. Firstly, the selection principle and approach of main environmental stresses (MESs) and key characteristic parameters (KCPs) are presented based on fault mode, mechanism, and ESs analysis (FMMEA). Secondly, reference stress events (RSEs) are constructed by dividing IES into three stress levels according to its impact on faults; and then the association model between integrated environmental stress event (IESE) and BIT output is built. Thirdly, an interval grey association approach to evaluate IES level is proposed due to the interval number of IES value. Consequently, the association output can be obtained as well. Finally, a case study is presented to demonstrate the proposed approach. Results show the proposed model and approach are effective and feasible. This approach can be used to guide ESs measure, record, and association. It is well suited for on-line assistant diagnosis of faults, especially IFs.     

利用CFD技术计算飞行器动导数

利用非定常流场数值计算方法模拟飞行器强迫俯仰振荡仅能得到俯仰力矩系数对迎角变化率和俯仰角速度的动导数之和,而动稳定性分析需要单独的动导数数值.为解决这个问题,利用滑移网格模拟强迫振荡运动,得到俯仰力矩系数对迎角变化率和俯仰角速度的动导数之和.利用旋转参考坐标系模拟定常拉升,得到俯仰力矩系数对俯仰角速度的动导数.利用旋转参考坐标系模拟匀速滚转,得到滚转力矩系数对滚转角速度的动导数.对有翼导弹和水上飞机进行了纵向和横向动导数的计算.计算结果与试验数据、文献数据以及其他方法得到的结果具有较好的一致性,表明提出的方法可用于复杂外形飞行器动导数计算.     

材料加工技术在低碳经济中的应用及发展

介绍了低碳经济形势下的薄坯铸轧、精密成形加工、闪光焊、无模成形、内高压成形以及其他先进成形加工技术,并展望了先进材料加工技术的发展趋势.     

三维打印技术在粉末材料快速成形中的研究现状评述

基于微喷射的三维打印快速成形技术,集CAD/CAM、数据处理、材料科学、微滴喷射和数控等多种技术于一体,是当前较成熟的快速成形技术之一。     

基于刃边法的星载相机在轨MTF测量精度分析

调制传递函数(MTF)反映可见光对地遥感系统在对地物成像过程中信号的扩散与削弱程度,是表达系统辐射性能的重要指标.文章对星载可见光CCD相机在轨MTF主要测量方法进行比对分析,通过数据仿真,重点对随机噪声、边缘探测与拟合等主要影响刃边法精度的因素进行了分析.分析结果表明,计算所用刃边法能够较准确地计算可见光遥感系统的M...     

光电技术在中国深空探测中的应用

文章简单回顾了中国深空探测已走过的历程和正在进行的项目,展望了今后的发展;分析了深空探测器及其有效栽荷对光电技术的需求;重点对中国已发射的月球探测器"嫦娥一号"、"嫦娥二号"中应用的光电技术和获取的成果,正在研制的"嫦娥三号"探测器中所应用的光电技术,月球探测三期和今后可能发展的深空探测项目中预计采用的光电技术的研制工...     

不同截面机身头部吹气方式对侧向力的影响

研究了机身头部法向吹气和具有不同指向角的喷管切向吹气对于不同截面的机身前体所产生的影响.在风洞中采用测力的方法给出了不同截面形状的非细长机身的实验结果.讨论了迎角、吹气方式、喷管指向角及截面形状对机身侧力的影响.实验表明,法向吹气和喷管切向吹气都是有效的控制手段,吹气对其中圆锥截面模型的影响最大,椭圆截面模型次之,对带棱截面模型影响最小.